1. Field of the Invention
The present invention relates to a control device for a legged mobile robot, such as a bipedal walking robot.
2. Description of the Related Art
As a technique for enhancing the stability of the posture of a legged mobile robot, which travels by moving a plurality of legs extended from a base body, the technique disclosed in, for example, Japanese Patent No. 3269852, has been proposed by the applicant of the present application.
According to the technique, a state amount deviation of an actual posture of the body of a robot from a desired posture is observed, and an operational moment (an operational moment about a desired ZMP) to be additionally applied to the robot is calculated according to a PD law (proportional-differential law) from the observed value of the state amount deviation as the feedback manipulated variable (control input) required to converge the state amount deviation to zero.
Further, the operational moment is divided into an actual robot manipulation moment to be directly applied to an actual robot and a model manipulation moment to be applied to a robot in a dynamic model for generating a desired gait of the robot.
In the actual robot, the motions of the actual robot are controlled by compliance control such that the actual motion of the robot follows the motion of a desired gait (desired motion) while generating the actual robot manipulation moment about the desired ZMP. Further, in the dynamic model, a desired gait of the robot is generated such that a model manipulation moment is generated about the desired ZMP.
Thus, in the case where the actual posture of the body of the robot deviates from a desired posture due to a disturbance or the like, a floor reaction force moment for eliminating the deviation is applied to the robot.
To determine a desired motion that allows the actual motion of a legged mobile robot to stably continue by using an appropriate dynamic model, the desired motion is required to be determined such that a variety of requirements is satisfied. Typical requirements are that a desired ZMP (the position of a desired total floor reaction force central point) does not deviate from a predetermined zone (e.g., a supporting polygon), and that the desired motion of the robot does not diverge, i.e., the desired motion enables the robot to accomplish continuous motion. Frequently, such a desired motion cannot be generated by analytical arithmetic processing. Consequently, there are many cases where arithmetic processing that requires relatively high arithmetic load, such as exploratory arithmetic processing, is required to generate the desired motion.
Hence, in the case where the motion of the robot is controlled especially while sequentially determining a desired motion of the robot in real time, the cycle of the processing for generating a desired motion frequently has to be set to rather long time in order to leave a certain allowance.
Meanwhile, in order to particularly achieve still faster motions of a legged mobile robot, it is considered desirable to effect the adjustment or correction of the desired motion of the robot to eliminate the deviation of the actual posture of the robot from a desired posture as quickly as possible.
However, if the cycle of the processing for calculating a desired motion has to be set to rather long time, as described above, then it is difficult to ensure high responsiveness in adjusting the desired motion when the actual posture of the robot deviates from a desired posture. This in turn inconveniently makes it difficult to achieve still faster motions of the robot.